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Beyond the basics for Li-ion safety?

I've been doing a lot of reading on lithium rechargeables and must admit, I'm terrified. I ordered some cheap batteries (trustfire protected) and charger (WF-139) and would like to ask a couple questions that have been on my mind. I really would like to get more expensive chargers and batteries, but I'm not "that" into lights yet that I'd like to take that 4x 5x price increase, and even then theres no guarantees.

To make sure I understand this, the main threat is the battery releasing poison gas, the gas building up in the tube, and one end of the light blowing off with extreme force, like a roman candle and likely catching fire. Are there any additional safety measures you could take to protect from this (aside from treating your batteries well), like making a hole in the flashlight body/clicky, or not screwing on your tailcap too tight?

The stories I've read that resulted in an explosion usually have a "non tragic" ending. No one got seriously hurt, at most suffered some light wounds but no fingers lost, no blindness, no house burning down, no death. That leads me to believe that even in a worse case scenario you are given adequate warning either from hissing or heat, to chuck that flashlight and yell grenade. Has anyone heard any tragic stories caused by lithiums in flashlight? What are some more warning signs?

I'm looking for some "above and beyond" safety tips. I'm a stickler for safety and would never forgive myself if something like a flashlight blew off my hand or burned down my home.

Re: Beyond the basics for Li-ion safety?

afaik, the released gasses when venting are not poisonous as such (at least in the low concentrations in this circumstance)

You could try drilling a hole in your light to vent, however this would eliminate any water-proofness, and wouldn't make a huge difference anyway... it might only blow up a little bit, or just shoot a 6 inch flame out the side if it went critical.

There are a few horror stories around, but seriously, there are hundreds of thousands of users of these type of cells, and millions, if not billions of people using lithium-ion worldwide. If it were that common, there would be far more stories to tell.

Check list:

1.) Good quality cells - Doesn't have to be AW, but it also wouldn't hurt.

2.) Good quality charger - Can be a cheapy if you want, but you should be aware of how it works, and how it charges. If it trickle charges, or if it will feed too much current etc. Again, better known brands might be better for a reason.

3.) Get a multi-meter - This is pretty much a "must have" item. Doesn't have to be super expensive, or super accurate, but has to be consistant. Get a baseline of your cells when they have charged (around 4.2V or below) and make sure they aren't going over that level on subsequent charges. If they do, consider step 4.)

4.) Chuck cells when they need to be - If a cell is over charged, or discharged, then get rid of it. If you have charged a cell to over 4.25V then its getting a bit dangerous, and if you over discharge a cell, then it is equally dangerous. Chuck it out, and get a new cell. They are cheaper than a new house.

5.) Use protected cells when possible - If you are new to the game, protected cells can be your best friend. Not only do they have safety features built in for when you are using them, but also when charging your cells. Can include overtemp protection, over charge/discharge, and usually include a vent for gasses.

6.) set up a charging area - a lot of us charge our cells in a metal flame proof box on a cement floor for a reason... if you are charging lots of high capacity cells, then you have higher potential for BOOM. Again, not a mandatory thing, but reccomended you at least get an area that you would consider safe to use

7.) Don't leave your cells unattended while charging. I know its a pain in the ass to charge a pair of 18650's for 5 hours, but if you leave them on overnight, you won't know how they are behaving. You should check for the temperature of the cell itself when charging, and check the charger itself. Expect a bit of warmth (10-20 degrees above body temp) but if it is too hot to touch, you got some trouble!

8.) Use the right cell for the job - if you have a high drain device, consider reading up on, and buying some quality IMR cells, if you need a cell that puts out a lower voltage, consider some LiFePO4 cells. Knowing the chemistry of the cells, and their limitations will make using and caring for your cells easier.

Lithium Ion cells have come a long way in safety, but generally the cheapest cells on the market, can also be the most volatile.

Anything I need to add?

mossyoak --> Dear God man, its your honeymoon, screw the flashlights, bring one or two and some backup batteries, and fill up all that extra room you have with condoms and alcohol.

Re: Beyond the basics for Li-ion safety?

I use AW protected cells, charge in Pila IBC on nonflammable surface, and use a multi meter. Don't give much thought to safety beyond that.

1) If max charge is slightly lower you will get longer life spans from cells. 4.2v is termination a lot of users go with. Charge often as letting voltage dip excessively is bad for service life too. Li-Ions are fine with simple top-offs.

2) Test cells when off charger.

3) You could use a box. Heat is enemy of all charging cells, keep this in mind. IMO a solid surface that will not burn and away from other stuff that could catch is ample.

Re: Beyond the basics for Li-ion safety?

off topic, i could have "burned my house down", and "crashed my car" by making stupid misteaks with ni-cd and ni-mh too.
some of it is just the Power, respect the power.
Because of the ability to have high current flows enough to short a wire out and start stuff on fire, and due to cheap batteries that had no physical protection, or vents or safety of any kind, i had a ni-cd explosion, and nice fire burning in the middle of the room :-) and one time due to a short , a battery pack started a nice little smoldering pile in the truck while driving down the road.

it doesnt have to be lithium, to have a lot of power in it, or to be a cheap piece of junk with minimal safety features.
kids have a lot of power too, just like batteries you dont leave them alone when there Playing :-)

know the specs, that is one thing, a person might read the "manuel" for something they want to operate correctally, but reading a spec sheet to see how to use the battery correct is not important? if there isnt a spec sheet :-) then . . . that is just like getting anything else without a manuel, you use the "Try And Fail" methods till you get it right. the fail part being the problem.

Re: Beyond the basics for Li-ion safety?

Thanks for the replies =)

I have a Dilemma now. I can charge them in my room where I spend most my time, OR in my garage on the concrete floor, but I'm not going to be standing in my garage for 5 hours and don't spend much time in there.

Re: Beyond the basics for Li-ion safety?

Re: Beyond the basics for Li-ion safety?

i had to quit putting them in the garage, when the quantity of solvent, gas, paint, oil, cardboard, wood, and other stuff that would "contribute" if ever an ignition occured, there was some point where the garage was no longer "safer" .
if you have it in a tall open container where it can not "fly out", and a small fire could occur in the container and it would not cause a problem, then it is likly to be very safe.
I guess i would rather see a fire start, then to have it build up before i saw it. but if the fire will be contained, then i dont need to see anything.

odd things to add , often homes do not have smoke alarms in garages, because it can be set off by the car exhaust , here they did not put the smoke alarm in the garage, only the fire sprinklers, and the sprinklers use a different valve releace too, i did not understand. I still have not put a smoke alarm in there, but i got electric doors where are my priorities

Li-ion does not like to be charged in extreeme cold, but i dont know what temp that is , if it is going to be extreemly cold, then you would want to know that spec item.

i have no intention on making that descision for you, you already know enough to be aware. and it doesnt do any good to be terrified, aware and proactive, beats making error out of fear.
Had one battery in pieces in the garage, using gloves and a face mask and doing all the "right things", while i was testing something else, the garage door opened and the other person drive right over the top of my battery. sooo, you have to decide. to many factors.

Re: Beyond the basics for Li-ion safety?

you know that one of the possible RARE problems, is when the solvent gas build up in containment .
or for other batts, hydrogen and oxygen gasses, which just love to recombine quick.
like there is a YouTube with an ammobox, this ammobox had a 3-4inch gaping hole in it, running a dryer hose out, and it still freaking "blew up" harshly because the device "contained" the gasses, and was capable of "increaing the compression" on ignition of the gasses.
that is why tall and open IMO is better than this idea of trying to shut it up in safes and all.

ya got the lithium ok, but you also have a solvent , and oxigination , and its like vaporised gasses kinda thing.
now it is unlikely that you can get the kind of activity that they do when doing it on purpose, but the gasses are still a concideration.
Whoosh is better than Boom, as long as woosh doesnt lead to ketching all the other stuff you left around on fire too.

Re: Beyond the basics for Li-ion safety?

I don't think the cell is ruined if it gets discharged below 3.7 volts, as long as it doesn't stay there long. If you have good cells, good charger, and a volt meter I think its fine to charge li-ion in the house, if you are in the same room. Li-ion are used in laptop battery packs, they aren't terribly dangerous, its just most flashlights don't have the electronics in them to prevent over discharging/charging. Li-ions in a flashlight are also safe if they are single cells, or multi-cells that are matched properly (voltage, manufacturer, purchase date, etc.). From my understanding they "vent-flame" most often while they are charging after being over discharged/over charged.

Re: Beyond the basics for Li-ion safety?

Plus
shorts or reverse charge, all good reasons for effective non-shorting Added curcuit protection.
and The internal to the cell itself "mechanical protection" the anode disconnect and PTC device, and for the gassing disconnect to work a good proper seal between the anode dis-connect device and the fixings in the cell.
and internal breakdowns and shorting internally, plating of lithium , which can be via bad cell, or improperly treated, or improperly made cell.

Re: Beyond the basics for Li-ion safety?

I have been using LiIon for a a few years and have never had a fire or explosion or even a hot cell, even when doing many charges and discharges.

With that said, I like them and has a couple of them. If an accident happens they will prevent a LiIon "explosion" to throw hot (burning) stuff around. But you might still get a local fire at the sack.

Also note that LiPo for RC use are more likely to explode than normal LiIon cells.

Re: Beyond the basics for Li-ion safety?

I still think all multi-cell Li-Ion lights should have a forward (bezel end) venting, one-time use safety feature, kinda like an airbag. You would lose your water proofness once it blows, but at least no one would be hurt and your light would still be intact. Then you could just buy a new "venting collar" that would slip in place of your old destroyed one... Why not? Hey... If anyone uses this idea, please cut me a little something.. like a free light and some inventing credits, hell, a small portion of your proceeds in sales... You listening Surefire??????

Re: Beyond the basics for Li-ion safety?

Maybe a latex condom kinda membrane that would swell so you would know when your're lights about to go - then the pressure would be released through the weakest point - the membrane, instead of blowing your tailcap out or blasting your 16340 cells out the bezel into your eight year old nephew's forehead. That way you could retain water proofness. The membrane would be cheap and easily replaceable. Flashlight companies.. if you want to hire me, I am currently looking for steady work. ;D

Re: Beyond the basics for Li-ion safety?

Re: Beyond the basics for Li-ion safety?

Originally Posted by tolkaze

afaik, the released gasses when venting are not poisonous as such (at least in the low concentrations in this circumstance)

You could try drilling a hole in your light to vent, however this would eliminate any water-proofness, and wouldn't make a huge difference anyway... it might only blow up a little bit, or just shoot a 6 inch flame out the side if it went critical.

There are a few horror stories around, but seriously, there are hundreds of thousands of users of these type of cells, and millions, if not billions of people using lithium-ion worldwide. If it were that common, there would be far more stories to tell.

Check list:

1.) Good quality cells - Doesn't have to be AW, but it also wouldn't hurt.

2.) Good quality charger - Can be a cheapy if you want, but you should be aware of how it works, and how it charges. If it trickle charges, or if it will feed too much current etc. Again, better known brands might be better for a reason.

3.) Get a multi-meter - This is pretty much a "must have" item. Doesn't have to be super expensive, or super accurate, but has to be consistant. Get a baseline of your cells when they have charged (around 4.2V or below) and make sure they aren't going over that level on subsequent charges. If they do, consider step 4.)

4.) Chuck cells when they need to be - If a cell is over charged, or discharged, then get rid of it. If you have charged a cell to over 4.25V then its getting a bit dangerous, and if you over discharge a cell, then it is equally dangerous. Chuck it out, and get a new cell. They are cheaper than a new house.

5.) Use protected cells when possible - If you are new to the game, protected cells can be your best friend. Not only do they have safety features built in for when you are using them, but also when charging your cells. Can include overtemp protection, over charge/discharge, and usually include a vent for gasses.

6.) set up a charging area - a lot of us charge our cells in a metal flame proof box on a cement floor for a reason... if you are charging lots of high capacity cells, then you have higher potential for BOOM. Again, not a mandatory thing, but reccomended you at least get an area that you would consider safe to use

7.) Don't leave your cells unattended while charging. I know its a pain in the ass to charge a pair of 18650's for 5 hours, but if you leave them on overnight, you won't know how they are behaving. You should check for the temperature of the cell itself when charging, and check the charger itself. Expect a bit of warmth (10-20 degrees above body temp) but if it is too hot to touch, you got some trouble!

8.) Use the right cell for the job - if you have a high drain device, consider reading up on, and buying some quality IMR cells, if you need a cell that puts out a lower voltage, consider some LiFePO4 cells. Knowing the chemistry of the cells, and their limitations will make using and caring for your cells easier.

Lithium Ion cells have come a long way in safety, but generally the cheapest cells on the market, can also be the most volatile.

Re: Beyond the basics for Li-ion safety?

If you could add:
Minimum voltage before cell damage?
Don't use multiple cells (e.g. 2xRCR123, try to use 18650 instead).

Originally Posted by tolkaze

afaik, the released gasses when venting are not poisonous as such (at least in the low concentrations in this circumstance)

You could try drilling a hole in your light to vent, however this would eliminate any water-proofness, and wouldn't make a huge difference anyway... it might only blow up a little bit, or just shoot a 6 inch flame out the side if it went critical.

There are a few horror stories around, but seriously, there are hundreds of thousands of users of these type of cells, and millions, if not billions of people using lithium-ion worldwide. If it were that common, there would be far more stories to tell.

Check list:

1.) Good quality cells - Doesn't have to be AW, but it also wouldn't hurt.

2.) Good quality charger - Can be a cheapy if you want, but you should be aware of how it works, and how it charges. If it trickle charges, or if it will feed too much current etc. Again, better known brands might be better for a reason.

3.) Get a multi-meter - This is pretty much a "must have" item. Doesn't have to be super expensive, or super accurate, but has to be consistant. Get a baseline of your cells when they have charged (around 4.2V or below) and make sure they aren't going over that level on subsequent charges. If they do, consider step 4.)

4.) Chuck cells when they need to be - If a cell is over charged, or discharged, then get rid of it. If you have charged a cell to over 4.25V then its getting a bit dangerous, and if you over discharge a cell, then it is equally dangerous. Chuck it out, and get a new cell. They are cheaper than a new house.

5.) Use protected cells when possible - If you are new to the game, protected cells can be your best friend. Not only do they have safety features built in for when you are using them, but also when charging your cells. Can include overtemp protection, over charge/discharge, and usually include a vent for gasses.

6.) set up a charging area - a lot of us charge our cells in a metal flame proof box on a cement floor for a reason... if you are charging lots of high capacity cells, then you have higher potential for BOOM. Again, not a mandatory thing, but reccomended you at least get an area that you would consider safe to use

7.) Don't leave your cells unattended while charging. I know its a pain in the ass to charge a pair of 18650's for 5 hours, but if you leave them on overnight, you won't know how they are behaving. You should check for the temperature of the cell itself when charging, and check the charger itself. Expect a bit of warmth (10-20 degrees above body temp) but if it is too hot to touch, you got some trouble!

8.) Use the right cell for the job - if you have a high drain device, consider reading up on, and buying some quality IMR cells, if you need a cell that puts out a lower voltage, consider some LiFePO4 cells. Knowing the chemistry of the cells, and their limitations will make using and caring for your cells easier.

Lithium Ion cells have come a long way in safety, but generally the cheapest cells on the market, can also be the most volatile.

Li-ion beginner primer

12/27/11: I have explained the abbreviations and battery chemistries a bit at the end of the LI ION BATTERY CHEMISTRY AND SAFETY section. I added some words about using a DMM at the end of the recommendations section.
12/26/11: Added A BIT MORE DETAIL ON CHARGING, after the charging section

Hi folks, on other forums I read, I often notice a lack of info on Li Ion batteries. Most disconcerting, people have experience with alkaline and Nimh batteries, and assume Li Ion care and feeding is as simple, and the consequences of a mistake similarly (usually) small. I wrote a quick beginner primer, that may actually be useful here too, though folks here tend to be a lot more knowledgeable. In the meantime, I'm asking for feedback on this: is it factually correct? Are there important details I left out? Is it useful? Some of the emphasis in the article has been lost -- I was able to underline important points, but that underlining has disappeared in this forum (I'll change to bolding later today).

I'm going to try to make this really short, which means I'll drastically simplify and generalize. If anyone things I've oversimplified to point that the information looks incorrect, let me know and we'll discuss changing it right here in the primer. If you just want to add detail, we should let those stay as follow-ups. The reader should know that I've simplified a lot, you should be checking places like battery university and candlepowerforums for more detail; I mostly want to jumpstart you into a place where you're vaguely safe.

WHY WRITE A PRIMER?
I'll tell you first, I'm a bit conservative when it comes to things like safety. For all the positives of Li Ion batteries, the downside is that the consequences of making a mistake can be serious -- explode in your light or burn down your house serious. On the other hand, let's keep some perspective: many people use these batteries in hobbies like RC, and homes aren't burning down left and right. That said, I don't want *you* to be the statistic. I look at Li Ion batteries like a firearm: understand and follow a few simple rules, and there's no reason to fear them. But these are not the no-brainer technology that alkalines are.

I'm going to discuss the very basics of batteries and chargers. I'm going to use some examples of specific products that I feel violate the rules. And I'm going to try to give you enough info to evaluate that claim on your own. I will make specific recommendations for beginners at the end.

WHY GO WITH LI ION?
• If you use your light a lot, rechargeables will be much cheaper to run in the long run, and easier on the environment
• Modern lights are increasingly running at higher performance with Li Ion rechargeables. For example, the current XML based V10R is running 150 lumens on a CR123 primary, but over 400 lumens on a RCR123 or 16340 (both terms for a li ion rechargeable).
• Even though lithium primaries have higher capacity than lithium ion rechargeables, when I walk out the door with my rechargeable, I know my light is at full charge. With primaries, I'm never sure, since I'm not going to replace a primary that seems to be running well just because I've used it for the past week, and I can't just top it up.

LI ION BATTERY CHEMISTRY AND SAFETY
There are multiple battery chemistries for Li Ion batteries. I am going to almost solely discuss LiCo, but there are other chemistries popular in lights such as IMR and Lifepo4. I will contrast with IMR occasionally.

The thing about LiCo batteries is that the chemistry is not safe. By not safe, I mean, conditions can occur where the battery goes into thermal runaway, at which point it can vent violently or explode. A safer battery chemistry might cause the battery to shut down under these conditions, but because LiCo batteries go into runaway, I am only going to be discussing protected batteries from here on out: those batteries with built-in protection including a protection circuit and other safeguards that shut the battery down and prevent other conditions that can cause problems. However, I'll note that I never rely 100% of mechanical protection, these are inexpensive parts that sometimes aren't perfect. Having a safety doesn't mean you can point a loaded gun at someone

IMRs, by contrast, use a safer battery chemistry, and so don't have protection circuits. But IMRs have lower overall capacity than protected LiCos. Still, as we'll see, IMRs have characteristics that can let them outperform LiCos under some circumstances.

A quick summary of the most popular chemistries:

LiCo (LiCoO2) aka ICR batteries:
• Are the batteries usually being discussed when someone mentions something like “protected AW 14500” without any other qualifiers
• 4.2V max charge, 3.7V nominal voltage
• Not a safe chemistry, so can be purchased with a protection circuit that guards against overcharging and over-discharging
• Higher energy density, but lower charge and discharge rates, than the other batteries in this list
• Are the batteries I use in lights that can handle 4.2V and do not demand a higher current than what LiCo can deliver
• Chemical composition is lithium cobalt oxide

IMR (LiMn204) batteries:
• 4.2V max charge, 3.7V nominal charge
• Safe chemistry, so is not available with a protection circuit. But that means the consumer must guard against overcharge and overdischarge themselves.
• Slightly lower energy density than LiCo, but can sustain much higher discharge and charge rates. I use these in lights that can handle 4.2V batteries but require a higher discharge rate than LiCo can handle, like some of the newer demanding XM-L lights
• Chemical composition is lithium manganese oxide

LiFePO4 aka IFR batteries:
• 3.6V max charge, 3.2V nominal voltage
• Safe chemistry, so is not available with a protection circuit. But that means the consumer must guard against overcharge and overdischarge themselves.
• Lower energy density than LiCo, but can sustain higher discharge and charge rates.
• Chemical composition is lithium iron phosphate

CHARGING
These batteries use a CC/CV charging algorithm, where in the first phase of charging, an initial constant current is used. When the battery reaches 4.2V, that voltage is kept constant, until the current dwindles to a percentage of the initial current ... and when that happens, the charge terminates. You may be as shocked as I was to learn that the vast majority of production chargers do NOT conform to the above well-known and manufacturer-approved specs. We'll talk about a few chargers that do, later. One thing we do want to do: make sure we use a charger that's been shown to use the correct algorithm. But we don't want to completely depend on correct operation: as a rule, put your charger on a relatively fire resistant surface, stay with it while it's charging, and take your batteries off the charger when the light turns green. Technically, we've improved our safety by using a battery with overcharge protection and a charger that uses the proper algorithm; but if those two things go bad (and let's face it, with your luck, they might ), bad things can happen.

The other thing to watch out for is that a li ion that's been discharged too low is not safe to recharge or use, in the light-your-house-on-fire sense. Again, we're talking about batteries with protection circuits that should protect against that, but those protection circuits cost a few cents and can go bad. Do not make it a habit of letting the protection circuit trip to tell you when to recharge. There's very little penalty for topping off Li Ion rechargeables, which is a nice feature of the technology, it means you can top off often. I suggest you do so. If the protection circuit fails to trip, you may be recharging from an unsafe voltage.

The other feature of recharging: you really don't want to recharge at over 1C for smaller LiCo batteries and .7C for larger ones – check your battery’s specs to see the safe charging rate for your battery. C stands for the capacity of the battery. For example, a protected RCR123 currently is usually rated at 750 mAh. That means you don't want to use a charger that uses a current of greater than 750 mA, and really, you should stick with .8*750mA=600mA. Note that IMR batteries have different charging specs, with rates nearly reaching 3C.

A few examples now: the highly rated Pila IBC charger has a charging current of 600mA. That means you're good with batteries as small as a protected RCR123. But you certainly should not charge a 10440 (350 mAh) or smaller on this charger. For those of you who followed the now-recalled Jetbeam charger, you may remember me being critical in those threads. That's because Jetbeam claimed 10440 support for this charger, even though the charging current for a single battery could be as high as 1000 mAh. That's nearly 3C, and way outside manufacturer safety recommendations!!! So, I hope you now know how to tell if a charger's charging current is safe for a particular Li Ion battery: look at the capacity written on the battery, and stick to the battery manufacturer’s recommendation; .7C will usually be safe, when in doubt.

For reference, below is a chart of a CC/CV charge. The interesting points:
• Current starts out constant, with voltage rising
• When voltage hits 4.2V, it gets held constant, while current diminishes
• Current reduces until it hits a cut-off threshold (50mA, in this case), at which point the charge terminates (current should be zero or close to it, at the cutoff).

Many production chargers miss the mark on a number of points, in particular, the final termination. This could lead to dangerous conditions,

A BIT MORE DETAIL ON CHARGING
Below is a graph of a charger that correctly follows a CC/CV algorithm, courtesy of HKJ of CPF. I include it so you can see what a charging cycle should look like. Again, many chargers do not follow the algorithm properly. Among the common problems: at the end of the cycle, the charger must terminate, but many chargers keep applying what is essentially a trickle charge, which is arguably a dangerous mistake, and a good reason to choose a charger which has been reviewed and proven to follow a reasonable approximation of CC/CV, and to follow good charging practices.

Below, what you see in the first portion of the graph is the CC (constant current) stage. In this case, the current is kept constant at 1.0A while the voltage rises. When the voltage hits 4.2V, the CV (constant voltage) stage starts, where 4.2V is applied and the current naturally falls. When the current matches the termination current, you see the charger terminate at the vertical yellow line – we know proper termination has been achieved because current drops to 0 abruptly at that spot.

Another good practice is to have some way to measure the voltage of your Li Ion batteries, to make sure they’re coming off the charger with safe voltages, that you haven’t discharged to an unsafe voltage, etc. The LiCo batteries we’ve been discussing have been spec’ed to charge to 4.2V when fully charged, plus or minus .05V. Note that battery voltage will settle down a few hundredths of a volt, in the couple of hours after it comes of the charger; you can see that happening in the graph above, when the voltage represented by the red line starts sagging a bit after the yellow line indicating charge termination. If your battery is older, or you’re using a spacer, you might see lower voltages, even below 4.15V. Using an inexpensive digital multimeter (DMM), or the voltmeter that’s integrated into your Cottonpickers charger, you can check these voltages. I particularly do not want to see batteries coming off the charger higher than spec; if that happens, it’s important to figure out why, and resolve the issue immediately. Below 1.5V, these batteries start forming shunts that can internally short the battery, leading to fire or explosion; if a battery gets down that low, I retire it.

USING (DISCHARGING) LI ION BATTERIES
LiCo batteries want to be discharged at no more than 2C (read the above section if you don't remember what "2C" means). For a 750 mAh protected RCR123, that means no more discharge than 1500 mA. IMR batteries can handle up to 8C. That means for a 16340 IMR at 550 mAh, no more than 4400 mA (4.4A). By knowing the current demand of a flashlight, you can tell how a battery will run.

More real-life examples. There are a couple of XML powered lights that run on a single CR123A or RCR123A/16340 to put out 400+ lumens. For example, Jetbeam and the Sunwayman V10R XML put out well over 400 lumens, and to reach that output, they are pulling well over 2A (2000 mA) from the battery. We know from experimenting, IMR batteries can outperform LiCo batteries in these lights, even though IMRs have lower capacity. Can you tell why, based on the discussion above? These lights are pulling way more than the manufacturer-recommended 2C for LiCo batteries, and those batteries sag quickly under the load. IMRs, which can handle the load, provide higher output for longer -- and the current requirements can be safely met by IMRs. I run an IMR in my v10r, and since IMRs do not have an overdischarge protection, I just take care to charge it often.

HOW DO I KNOW THE SPECS ABOVE?
You'll need to research some of the specs above yourself. I get the battery's manufacturer recommendations right from them. For example, AW posts the charge and discharge ratings on his batteries right on his forsale page on cpfmarketplace. I read reviews of chargers and lights to determine things like whether a charger is following the correct algorithm, what its initial charging current is, what a particular light's current draw on high is, etc. I learned most of what I know from the battery section on CPF, a good place for more advanced topics. I strongly suggest you be self-sufficient in determing safe ranges for your batteries and chargers – as I outlined above, there are flashlight and charger manufacturers making recommendations that are contrary to the recommendations from the battery manufacturers. I typically take the battery manufacturer’s recommendations as primary, and will not use a battery in a light or charger whose specs are in contrast with the battery manufacturer’s safe ranges.

RECOMMENDATIONS FOR BEGINNER SETUPSLi Ion technology is not the place to cheap out. Buy quality from the beginning for both safety and top performance. Here are the recommendations I make to my friends who are just starting:

Buy your protected LiCo or IMR batteries from these manufacturers, who have proven to have very high quality high-performing batteries:
• AW
• Redilast
• Callie's Kustoms

Buy your charger from these manufacturers, who have been shown in reviews to use proper CC/CV algorithm with proper termination:
• Pila IBC: use this to charge 1 or 2 batteries at 600mA
• 4sevens: single-bay charger, switchable between 500mA and 1000mA charging rates
• Cottonpickers: uses clips and magnets instead of a bay, and works off a USB port. You can order multiple configurations which have different charge rates. For example, I have a charger that I can set to 200mA or 500mA charge rates, to handle relatively bigger or smaller batteries (this is the only charger I'd use to charge a 10440, since I can charge that at a safe 200mA rate). This charger can also be bought with a built-in voltmeter so you can see the voltage on your batteries.

I specifically avoid and do not recommend any of the products from the *fire companies, etc., in my opinion they've been shown to have inconsistent quality. I'm not claiming the ones above are the only safe choices, but just ones I personally feel good about.

You also want to have a way to check the voltage on your batteries. An inexpensive Digital Multimeter (DMM) is generally good enough. The built-in voltmeter on a Cottonpickers charger is good as well. Thus armed, you can:
• Check the voltage of your batteries off the charger, to make sure they’re not being dangerously overcharged
• Check the voltage of your batteries after use or long-term storage, to see if the voltage has dropped dangerously low (<1.5V), or if the protection circuit has tripped (0V).
• In multi-battery lights in which the batteries are in series, you can try to ensure you are using two batteries with about the same capacity, which will help avoid dangerous conditions that can occur when batteries are not balanced.